Apparatus for concentrating nitric acid



Aug..1`1, 1931. HECHENBLEIKNER 1,818,711

APPARATUS FOR CONCENTRATNG NTRIG ACID Filed' Feb. 24, v1928 2 sheets-sheet 1 l NvENToR 9 Z ORNEYS Aug. 11, 1931. l. HEcHl-:NBLEIKNER 1,818,711

APPARATUS FOR CONCENTRATING NITRIG ACID Filed Feb. 24, v1928 2 Shee's-Shee'cl 2 INVENToR Patented 1,1,` 1931 UNrrsDfsTATss PATENT OFFICE INGENUIN HECHENBLEIINEB, OF NORTH CAROLINA, SIGNOR BY IEBN E ABSIGNIENTB, TO CHEMICAL CONSTBUCTIQN OOBPORATION, A CORPORATION F DELAWARE .APPABATU FOB CNCENTBATING NITBIG ACU) application ma rebmry a4, ma semi no. maar.

This invention relates to a method of and apparatus for treating nitric acid, and has special reference to the provision of an improved method of concentrating aqueous ni- 6 tric acid and ofseparating the same from an admixture of aqueous nitric acid and a dedrating agent such as concentrated suluric'acid. i AV number of methods have been employed l0 in the arts for concentrating aqueous nitric acid or' for separating the same from an admixture of the aqueous nitric acid with sulphuric acid, the separation or/ and concentration of the nitric 'acid being elected either by external or internal heat treatment. Y

In one o-'these known internal heat treat;

ment methods, the aqueous nitric acid in mixture with sulphuric acid or other suitable dehydrating agent, is passed a ainst a coun- 2 ter-flowing 'current of steam, t e conditions of operation being such that highly concentrated vapors of nitric acid are obtained, the

aqueous content thereof being absorbed and retained by the dehydrating agent. While nitric acid of substantially high strengths may be thusobtained, this method suers the disadvanta e that the sulphuric acid is un dulydilute by the steam used in the process, which steam when converted into water, is absorbed bythe sulphuric acid.

In another of these known internal heat treatment methods, theacid mi'xture is passed downward through a column through which hot-air or other gases are assed upward and counter-current to the acid flow the -hot air or gas supplying the heat for distilling oli the nitric acid. rlhis method, however, is attended with a number of objections, since the air must not be too hot, due to its effect in causin local overheating and decom osition of t e nitric acid, and control o the temperature of vthe air requires the use of a large uantity of air and .apparatus of substantia m itude, and since furthermore the nitric acid vapqr is diluted with the air or other gas used, and ofttimes contaminated f thereby, the dilution interfering with the subsequent condensation of the nitric acid va ors. l

iethods of supplying the .distilling heat -heat treatment.

' to the mixture externally of the concentrating aware, has been found of such eiciency asto warrant commercial success. In accordance with one suggested method the admixture of acids .is passed through a vertical pipe containing a fillin mass, and the ipe 1s heated from the outside. In this met od, however, 'it is diilicult to obtain a uniform distribution of the mixture in the concentrating tower so that local overheating and decomposition'of the nitric acid occurs this diilculty-being accentuated by the inability ofv applying a uniform heat treatment to the acid mlxture. Moreover, this method also necessitates .apparatus of large dimensions resulting in complexity of operation and high construction and upkee costs. To avoid these diiculties, it has a so been 'sug-v gested to subdivide the heat treatment by n employinga tpluralityof retorts or concentrating c am ers, usm either intermittent or continuous steps lo supplying the acid mixture to the concentrating retorts; but for one reason or another, none of these methods has received favorable adoption. f

The prime desideratum of my present invention centers about the provision of an improved external heat treatment method of concentrating the nitiic acid which is characterized by the elimination of the aforesaid disadvantages inherent in and resulting from these rior methods of concentrating the nitric acid by either internal or external In accordance with the princi les of my present invention, the mixture o aqueous nitric acid and dehydrating agent, 'such as sulphuric acid, is continuously assed through a series of concentratiow therein of nitric acid vapor distilled in each of the retort chambers, the distilling heat being supplied by a heating medium applied' to each of the several retorts of the series, the arrangement Vof the parts and the operationof the system being such uni'- moet? 9 practice o formly concentrated nitric acid is produced of high strengths and without the other objections residing in the air heat treatment method, and without 5 unduly diluting the sulphuric acid, as is the rcase with the steam heat treatment method.

To the accomplishment of the foregoing and such other objectsas will hereinafter appear, my invention consists in the prothe steps of the processes, the apparatus and elements thereof and the relation one to theother as hereinafter more articulariy described inthe claims, reference being had to the ac- 15 companying drawings which show the pre# ferred embodiments of my invention, and..

in which: .y Fig. 1 is a front elevational view of one form of apparatus thatmay be usedinthe the method,

gig. 2 is a side elevational viewl thereof, Fig. 3 is an elevational view of a modified form of apparatus that ma be used 'in'.the practice of themethod, with .parts fof-[fthe apparatus broken away to lshow theinternal construction thereof.

Referring now more in detailtothe drawings and having reference first toFigs. land 2 thereof-, the apparatus is shown `to [comprise a series ofretort chambers 10, 1 0 which may beinthefforxn of elongated pipes arranged l.ing?'substantially vertical'v 'formation foi the purpose of conserving plant space, said retort-, uchambers being connected in series or cascade by the end elbow pi s 11, 11z the :uppermost or first retort cham r 10 being provided with a feed inlet 12 having a receptacle top 13 for reoeivin an' admix- .0 ture of aqueous nitric acid an strong sulphuric acid, andthe last or lowermost retort chamber ofthe series being provided with an outlet 14 for the sulphuric-acid or other dehydrating agent the said outlet communieating with the sulphuric acid tank 15.

vEach of the retort chambers 10 is constructed to "'rovide a long and shallow receps 'tacle for ho ding va shallow body of the acid admixture, theY construction being designed 5 to aford 'an extended surface or area of treatment having a substantial volume. This is accom lished by the design and constructron of e retort chambers and by the p rovision of dams 16, 16 arranged at the discharge' end of each pi chamber,K the level of the acid admix'ture in each chamber beingdetermined by the height of` these dams, an v the dams controlling vthe overflow movement ofthe acid mixture from one chamber 10 tov 9i. the next chamber 10 therebelow. The 'arrangement and construction of the retortVV as well as the manner of interconnecting the Vsaine in 4cascadeby the elbows 11 are such that spaces are provided in the 05 several retort chambers above the level of without contamination and sought to be efined dicate uppermost chamber 10 of the series, the said duct being connected to suitable vapor condensing apparatus of any improved type known in the art.

By reference to Fig. 1 of the drawings, it will benoted that the dams 16 form means -.for determining the level of the liquid treated in a retort and for controlling theo'verlflow movement of the liquid from one retort `chamber to the next retort chamber of the "series, and that each such dam with its as-A sociated connecting elbow 11 forms a spillway for 'spilling the liquid over from one retort chamber to the next lower retort chamber of the series. y This s illway func- -tions to break up the body of t e adgnixture treated in a retort as the adminture moves from one retortA to the next lower` retort of the series, and this breaking up of the body in producing a trickling iiow of` thefadmixture produces a large surface of agitation which results in a eat liberation of the gases or va ors at t e pillways. This intimate brea ing up of e liquid increases the acting surfacefor reabsoibmg body also any water which may be d iven of lby the e excess heat in any of the low r retorts.

For'distilling or driving oil' the nitric acid vapors from the acid mixture, i. e.' for denitratin the same each of the retort chambers 10 is provided with means for supplying heat externally thereto; and I have ound that the heat treatment may be accomplished with great eiciency by providing each of the pipe retorts 10 with a jacket 18 aixedto the pitpe retort in any desired way, as inin the drawings, the series of jackets 18 bein preferably connected in series or egscide the interconnecting pipe sections a duid heating medium, such for exam le as hot oil, the flow of the heating medium ing referably counter-current tothe acid 'flow in the retorts, the inlet for the heating meditherefore provided at 20 and the` um being outlet a 21.

An important desideratum in an a paratus of the nature thus far'described is t e regurature ofthe se arate relation 'of the tem v tort chambers. is4 regulation o temperature must be progressive, for all of the pipes land definite` gradients should -be observed.-

'Thus if the temperature is too highin thev lastpipe retort'of the series, water will be evaI orated which has to ,becondensed in the lll hrough these jackets is conducted v lll ear ier or upper pipe retorts. On the other v hand,- -if the temperature is to'o low, in-

sucient denitrationltakes place. The temv filled with the acid admixture which` liovv's `continuously from one chamber to the next, each chamber being subjected toan intensel and uniform application of heat derived'froin the fluid heatingmedium.A A large surface perature of the last or lowermost pipe ofthe series requiresA to be controlled with considerable finesse. This is accomplished by the invention as a result of the rovision of Ithe separage jackets 18 indivi ual to the heating or retort chambers, each chamber bein separately heated. The use of the i n divi ual heating jackets is thus superior to the use of a common furnace for the retorts as an operatin s stem. Furthermore, the

use ofsuch indivi ual heating jackets offers j of asubstantial volume of the acid admi-attire is thus alwa s under a. uniform treatment',

resulting in t e generation in each` chamber or retort of nitric `acid vapors, thevapor's.- in one chamber joinin .those generated. .in the next adjacent chamer thereabove and Iflowing 'countercurrent to the acidiiow .the vaors having exit atvv the discharge Aduct y17.

-referably th gretst heatis supplied at the lowermostconcentrating chamber 10 so that all of theresidualnitric acid therein i-s driven i off and` so that `a high heat eiiiciency is pro-v duced. By virtue of the continuous path provided by the successive chambers for the vapor flow, any water driven off in the lower yretorts b the heat is reabsorbed by the relatively co d strong acid 'over which it passes in the upper retorts so that only concentratedl nitric acid is produced in the condensers, this being a very important object attained by the process.

-. Preferably the retort pipes 10 are made of an acidroof iron, such as `iron containinfr silicon, own in the trade as. Duriron Corrosiron, Tantiron, etc. The starting sulphuric acid may be of about 92% strength anx the finishing sulphuric acid may leave at A about 80% strength; and where an acid-proof iron is employed the process may be re ulated to rmit the finishing acid tc be o lower strength,such as about 66%. Where these lower strengths are permitted, it will be understood that in view *of the absence lof any steam as an`internalheating medium, greater vuantities of nitric acid may be treated and gbtained for equalv amounts and ra'dients of sulphuric acid as compared Wit the' steam Yheat treatment method. In lieu of emplo ing hot oil as the heatingfiuid, I may use a igh pressure steam of su cient temperature. Al-

so, in order to reduce theboiling point of the acid, to facilitate denitraticn may subject the spaces above the acid level in the chambers to vacua. The temperature of the heating fluid is preferably regulatedl so that the su phuric acid at the exit of the system is heated to substantially its boiling point.

AWhile' I have shown vthel retorts arranged in substantially vertical formation to secure economy of plant space, it will'be apparent that' this arrangement may be altered.

Referring now to Fig. 3 of the drawin s,

I show a modified form of apparatus or practicing the process of the invention.

this form of the invention I provide a plurality of retort sections 22, 22 stacked in vertical formation, each providing a receptacle "for a shallow body of the acid mixture, connected together internally for acid iiow communication, each of the retort sections 22 being rovided with an annular heating space' whic maybe generally described as a jacket 23,- the said jackets being interconnected in cascade by means of the pipe sections 24, 24.

The u permost retort section 22 is presided 9 with t e acid feed inlet 25 and the vapor exit duct 26, and the lowermost retort section 22 is provided with the sulphuric acid outlet 27 communicating with the acid tank 28. i

The retort sections 22 may be made in the form shown in Fi ..3 so' that the vsections may be nested toget er; and the said sections are constructed so as to provide' for the continuous flow of acid downwardlyand the con- A tinuous counter-current iow of the distilled vapors upwardly. To achieve these results, each retort chamber 22 is shaped to provide an annular dished portion 28 having anoverflew dam 29 and a se arate dished section 30, the riphery 31 o which also forms an over ow dam, the said separate dished section l30 bein supported within the retort chamber in t e manner indicated in Fig. 3 of the drawings. With this construction it will be understood that the overflow from an annular dished container 28 of one chamber 22 drips or flows onto the dished section 30 ofy the next succeeding chamber 22 and the overflow from the dished section 30 of a chamber drips or flows onto the annular dishedv con tainer of the same chamber 22. It will also be seen that the jacket 23 su plies an intense .and concentratedheat uni ormly over the surface of vthe fannular dished container under treatment. The counter-current How of the distilled vapors 'moves through the clearances and spaces provided by and be'- ween the batch containers for the acid mixure. v

The method of practicing the recess withv either form of apparatus descri ed and the 4many advantages thereof Will, in the main,

be fully apparent from the above detailed description thereof. It will be further appaia 'ent that Awhile I have shown and described changes and modifications may be made .in

from the spirit of the invention, de ned in the structure disclosed without de arting the following claims.

I claim: f

1. An apparatus for separating nitric acid from` an admixture of aqueous nitric acid and a dehydrating agent comprisin a plurality of enclosed retort chambers, o struction means to obstruct and to retain in each chamber a body of liquid which is shallow but of ap reciable depth, means so connecting the cham ers in cascade as to cause liquid flow in one direction `whilepermitting gaseous or vapor iiow in the reverse direction over the tops of the shallow bodies of liquid, means ini' dividual toeach of said chambers for supplyin a heatin medium externally to said cham ers, a fee inlet for the acid and dehydrating agent for the series of chambers,l

an outlet for the dehydrating agent assol lciated with the last chamber of the series,

and an exit duct for the nitric acid vapors associated with -the first chamber of the series.

2. An apparatus for concentrating equeous nitric acid and for separating the same from an admixture of aqueous nitric acid and concentrated sulphuric acid comprising a plurality of.` pipe-shaped retort chambers arran ed inf vertical relation, obstruction means to ostruct and to hold in each of said chambers a body of liquid vwhich is shallow but of appreciable depth', means connecting the pipe chambers in cascade for gravitational liquid iow communication, the spaces in said chambers above the shallow bodies of the liquid ladmixture and the said connecting means also defining acontinuous path for the flow of nitric acid vapors in a reverse direction relative to the flow of liquid, means for sup lying a heating medium externally to said cxambers suicient to drive oi the nitric acid as nitric acidvapors, a feed acid inletfor the series of chambers, an outlet for the dilutedsulphuric acid associated with the lowest chamber of theseries, andan exit duct for the nitric acid vapors associated with the topmost chamber of the series.

3. An apparatus for se arating nitric acid from` an admixture 'o ueous nitric acid and sulphuric acid comprising a plural-A ity of enclosed retort chambers arrangedl in substantially vertical formation, obstruction means to obstruct and to retain in each chamber a bod of liqliid which is shallow but of appreciable dept means so connecting the chambers in' cascade as to cause liquid ow in one direction while permitting gaseous or vapor How inthe reverse direction over the tops of the'shallow bodies of liquid, heating jackets for said retort chambers, means for supplying a fluid heating medium to said jackets for externally heating said cham'- bers, a feed acid inlet for the series of chambers, an outlet for the sulphuric acidk associated with the last chamber of the series, and an exit duct for the nitric acid vapors associated with the first chamber of the series.

4. `An apparatus for separating nitric acid from an admixture of aqueous nitric acid and a dehydrating agent comprising a plurality of enclosed retort chambers, obstruction means to obstruct and to retain in each cham- -ber a body of liquid which is shallow but of of chambers, an outlet for the dehydrating agent associated with the last chamber of the series, and an exit duct for the nitric acid vapors associated with the first chamber of the series.

5. An apparatus comprising a series of retort chambers each adapted to hold a shallow body of a liquid to be treated, connecting members joining the chambers for continuous .liquid v4and intimate vapor iiow inter-communication, each of said retort chambers being provided at its discharge end adjacenta connecting member with means determining the level of the liquid treated in a retort and controlling the overliow movement of the liquid from one .retort chamber to the next retort chamber of the series, eachsuch means and its associated connecting member defining a spillway for spilling the liquid over from one retort chamber to the next lower retort chamber of the series.

6. A concentrating apparatus comprising aseries of pipe retort chambers each adapted to hold a shallow body of a liquid to be concentrated, connecting members joining the chambers for continuous liquid and vapor 'ilow inter-communication, each of said pipe retort chambers being provided at its discharge end adjacent a connecting member with a dam, each dam' determining the level of the liquid treated in a retort andcontrolling the overiow movement of the liquid members joining the chambers for continuous liquid and intimate vapor flow intercommunication, each of said retort chambers bc-V ing provided at its discharge end adjacent a connecting member with a dam, each dam determining the level of the liquid treated in aretort and controlling the overflow movement of the liquid from one retort chamber to the next retort chamber ofthe series, and

each dam and its associated connecting member defining a spillway for spilling the liquid chambers being provided at its discharge end with means determining the level of the liquid, treated in a retort and controlling the overflow movement of. the liquid vfrom one retort chamber to the next retort chamber of theseries, each such means and its associated connecting elbow defining a spillway for spilling the liquid over from one retort chamber from anadmixture of aqueous nitric acid and sulphuric acid comprising a series -of elongated enclosed pige retort chambers, obstruc'- tion means in eac adapted to obstruct and to hold therein a long body of the admixture which is shallow but of appreciable depth,

means so connecting'the chambers in cascade as to cause continuous liquid flowl in one di` rection while permitting continuous vapor dow in the opposite direction over'the tops of the shallow bodies of liquid, a heating jacket `for each-'retort chamber .of the series whereby said chambers ma beindividually and separately heated, an means for supplying a fluid heating medium to said jackets or externall heating said chambers. i

Signed` at ew York in the county of New' York and State of NewY York this 15th day of Februar A. D. 1928.

IN GE I'N HECHENBLEIKNER.

to the next lower retort chamber of the series, and external Y heating means individual to each of the retort chambers for heating the l -v same;

' 9. An apparatus for separating nitric acid from an admixture of aqueous nitric acid and sulphuric acid comprising a series of enclosed retort chambers, obstruction means in each adapted to obstructand to hold therein a body of the admixture which is shallow but of` appreciable depth, means so connecting the chambers in cascade as to cause continuous liquid ow in one direction while permitting continuous vapor flow in the opposite direction over the tops of the shallow bodies of liquid, and external heating means individual to each of the retort chambers for heating the,

' same.

I depth, means connecting the chambers in cas-' 10. An apparatus comprising a series of enclosed pipe shaped retort chambers, obstruction means in each adapted to obstruct and to hold therein a long body of a liquid to be treated which is shallow but of appreciable cade for continuous liquid flow communica-l tion, the spaces in said chambers above the shallow bodies of the liquid and the said connecting means defining a continuous path for the flow of vapors evaporated fromV said liquid, heating jackets for said retort chambers, a heating jacket being individual to each. l

retort chamber ci the series, and means for supplying a uid heating medium to said jackets for externally heating said chambers. 11. An-apparatus for separating nitric acid ist' 

